This invention relates to a differential line system for sending and receiving serial data. Many data transfer systems are currently in use, and most send a signal which is referenced to ground at the sending location and then the received signals are reconstructed with reference to ground at the receiver location. The two grounds are seldom the same and therefore the information conveyed in the transmitted signals is subject to error.
The ground potential in the basement of a typical high-rise office building may vary significantly with respect to ground potential at the top floor. Similarly, when transmission lines are long, great differences in ground potential can and often do occur. In such instances, significant errors can result when the received data is reconstructed for use.
The present invention utilizes a pair of differential lines for data transfer and reconstructs the data by measuring a current difference between the differential lines rather than the voltage difference measured with respect a ground.
More particularly, the present invention utilizes a pair of differential lines, interfacing the sending end of the differential lines with serial data out and control signals and for interfacing the receiver end of the differential lines with a serial data input.
The interface circuitry at the transmitting end of the differential lines enables highly reliable data signals to be sent over the differential lines and the receiver interface insures that the transmitted signals are accurately reconstructed to provide accurate serial data into the receiver station regardless of even relatively large variations in ground potential between sending and receiving locations.